Abstract
Traditional coloring techniques used in Japanese metal crafts, such as niiro and iroage, are explained. In niiro for copper-gold alloys, a Cu2O layer in which gold particles are dispersed is formed on the alloy surface. This gold alloy is colored through absorption and reflection of light by gold particles in the layer. Besides coloring, this layer functions to prevent corrosion. In iroage for gold-silver alloys, silver dissolves selectively by heating after a chemical is applied on the metal surface. As a gold-rich layer is formed on the gold-silver alloy surface, the gold color is produced.
